1. Technical Field
This invention relates generally to internal combustion engines, and more particularly to monobloc pistons.
2. Related Art
It is known that internal combustion engines, and particularly diesel engines, utilize monobloc construction pistons having a fixed skirt formed as one piece of material with the piston. The skirts typically have a rectangular configuration extending continuously between opposite pin bosses downwardly to a substantially straight bottom edge. Although the skirts are generally effective in guiding the piston within a cylinder bore, they have inherent drawbacks. First, being constructed as a continuous rectangular wall of material, the skirts increase the overall weight of the piston. The increased weight can decrease the useful life of associated components by imparting increased inertial forces thereon, while also reducing the fuel economy of the engine. Further, increased area of the skirts causes friction against the cylinder liner, thereby further reducing the useful life and fuel economy of the engine. In addition to these drawbacks, having a continuous rectangular skirt wall reduces the flexibility of the pin bosses. Accordingly, the pin bosses unable to flex with the wrist pin during a stroke of the piston, and thus, increased friction results in the wrist pin joint and pin bores. Further yet, manufacture of the skirts can prove difficult in that the processes used to form them must provide for precise formation of wall contours and thicknesses over the full skirt area.
Some attempts have been made to reduce the skirt area and weight, including forming skirts with recesses extending from the lower surface upwardly to the pin bore axis, however, these efforts fall short of attaining a maximized reduction in skirt area and weight, and the aforementioned friction issues still remain in large part between the skirt wall and the cylinder bore, and also in the wrist pin joint and pin bore areas.
A monobloc piston manufactured according to the present invention overcomes or greatly minimizes the drawbacks resulting from at least those problems discussed above, thereby allowing engines to operate at an increased performance level, while reducing their fuel consumption, oil consumption and exhaust emissions, besides prolonging their useful life.